Email via airmail.net dated 2098?

This morning's emails delivered via airmail.net all are dated in 2098. Those marked dispatched on the evening of 12/30/1999 are delivery dated "Tue 12/30/2098". Those dispatched on the evening of 12/31/1999 are delivery dated "Wed 12/30/2098". Based upon the contents of the messages, including attached photos, the dispatch dates appear correct. Any known explanation?